XI. SUMMARY 126 BIBLIOGRAPHY 131 INDEX 135 LIST OF MAPS FACING PAGE Map showing the range of the American Golden Plover, with its known migration route 76 (From _The National Geographic Magazine_.) Map showing the evolution of the migration route of the American Golden Plover 78 (From _The National Geographic Magazine_.) Map showing the evolution of the migration route of the Eastern or Pacific Golden Plover 80 (From _The National Geographic Magazine_.) Map to show that a bird leaving Norway, near Aalsund, might be carried round the British Islands in twenty-four hours. The arrows indicate the actual directions and force of wind at the times marked during a slow-travelling circular storm in autumn 1901. Speed of bird about twenty-five miles per hour 98 * * * * * THE MIGRATION OF BIRDS CHAPTER I MIGRATION OF BIRDS Migration is the act of changing an abode or resting place, the wandering or movement from one place to another, but technically the word is applied to the passage or movement of birds, fishes, insects and a few mammals between the localities inhabited at different periods of the year. The wandering of a nomadic tribe of men is migration; the mollusc, wandering from feeding ground to feeding ground in the bed of the ocean, migrates; the caterpillar migrates from branch to branch, even from leaf to leaf; the rat leaves the ship in which it has travelled and migrates to the granary; we pack our goods, hire a removing van and migrate to a new abode. The word migration thus applied may be literally correct but it fails to convey the generally accepted meaning, and the expression Bird Migration suggests periodical and regular movement, the passage as a rule between one country and another. The popular application of a term does not do away with the need of definition, especially as there are many complicated phases of migration. The migration of birds is as a rule between the breeding area or home and the winter quarters, but there are many migrants which never reach breeding quarters in spring, and many others which leave the regular breeding quarters or the place of residence in winter to perform a very real migration under peculiar stress of circumstances. Again the spasmodic movements of certain gregarious species, which at irregular intervals change their location in large numbers to take up their abode in another part of the range, is really migration, though it is now usually described as irruption, incursion or invasion.